The present invention relates to special reproducing systems in rotary recording medium reproducing apparatuses, and more particularly to a special reproducing system in a reproducing apparatus for reproducing a video signal from a rotary recording medium on which the signal has been previously recorded along a spiral track by use of a reproducing transducer, where the above system is capable of moving the reproducing transducer to an adjacent track to perform a special reproduction wherein the motion of the reproduced picture is different from that upon normal reproduction, without introducing irregular and unstable motion.
A new information signal recording and/or reproducing system has been proposed in a U.S. patent application Ser. No. 785,095 entitled "INFORMATION SIGNAL RECORDING SYSTEM" filed Apr. 6, 1977, and now U.S. Pat. No. 4,331,976, issued May 25, 1982, of which the assignee is the same as that of the present application. According to this proposed system, the recording system forms pits in accordance with the information signal being recorded along a spiral track on a flat disc shaped recording medium (hereinafter referred to as disc), without forming a groove therein. In this reproducing system, a reproducing stylus traces over along this track thereby to reproduce the recorded information signal in response to variations in the electrostatic capacitance.
In this system, since a groove for guiding the reproducing stylus is not provided on the disc, pilot or reference signals should be recorded on or in the vicinity of a track of the information signal, such as a video signal, on the disc. Upon reproduction, the reference signals are reproduced together with the video signal. Tracking servo control is carried out so that the reproducing stylus accurately traces along the track in response to the reproduced reference signals.
By the use of this previously proposed system, there is no possibility whatsoever of the reproducing stylus or the disc being damaged since the recording track has no groove. The stylus can trace the same portion of the track repeatedly many times, whereby a special reproduction such as still, slow motion, or quick motion reproduction becomes possible.
Thus, in a U.S. patent application Ser. No. 4,813 entitled "SPECIAL REPRODUCING SYSTEM IN AN APPARATUS FOR REPRODUCING VIDEO SIGNALS FROM A ROTARY RECORDING MEDIUM" filed Jan. 19, 1979, now U.S. Pat. No. 4,340,907 issued July 20, 1982 of which the assignee is the same as that of the present application, a special reproducing system in a disc reproducing apparatus was proposed which is capable of performing a special reproduction in which a picture having a motion different from that upon normal reproduction is obtained in an excellent manner.
The special reproducing system comprises a reproducing element for tracing the track of the disc and picking up the recorded signal, a tracking control mechanism for operating in response to skip pulses applied thereto to cause the reproducing element to shift to an adjacent track turn of the spiral track thereby to undergo skipping, and a skip pulse generating circuit for generating skip pulses with timings corresponding to the vertical blanking period positions of the recorded video signal, where the skip pulses are of a number corresponding to an operational mode for carrying out a special reproduction differing from normal reproduction at every rotational period of the rotary recording medium, and supplying the skip pulses to the tracking control mechanism. The reproducing element is skipped to an adjacent track turn within the vertical blanking period of the recorded video signal, by the tracking control mechanism responsive to the skip pulses.
Accordingly, the noise introduced when the reproducing element moves to an adjacent track does not appear in the picture, and a special reproduction such as still reproduction, slow-motion and quick-motion reproduction in the forward direction, and normal-speed, slow-motion, and quick-motion reproduction in the backward direction can be performed in which a fine picture is obtained.
Hence, due to realizing conditions such as the recording capacity of the disc, the rotational speed of the disc, and the diameter of the disc, normally, the system is standardized wherein a video signal amounting to two frames, that is, a video signal amounting to four fields is recorded per one track turn (spiral track part corresponding to one revolution of the disc). When a still reproduction is performed by reproducing only the same track of the disc recorded according to the above standard, the image of the still picture flickers and the reproduced picture becomes unpleasant to watch when the movement in the picture where the still reproduction is performed is fast, since the information contents (pictures) of two different frames are alternately reproduced.
Accordingly, in order to overcome the above described problem, a system was proposed in which a video signal amounting to one frame of information is recorded per one track turn, by recording a video signal having the information content of the preceding frame into the subsequent frame. That is, the same information content for the preceding one frame is repeated in the subsequent frame, in every track turn. According to this system, flicker is not introduced in the image of the reproduced picture as in the above case, because the information contents of the same frame are repeatedly reproduced upon still reproduction.
However, when a disc on which a video signal having information contents amounting to one frame is recorded in groups of two frames per each track turn as described above, is reproduced in reproduction modes such as a double, triple, and quadruple speed forward quick-motion reproductions, information contents amounting to one frame are completely dropped out every plurality of frames of the reproduced signal. Hence, in this part of the reproduced signal where the dropout of information contents occur, the following field contains information contents of a field which is two fields after, that is, a field skipped by one field from a certain field. Accordingly, in the quick-motion reproduction modes, the movement in the reproduced picture is not smooth, and is irregular and unstable.